The proposed study will explore the effects of a stringent new alcohol control bill in Thailand on HIV risk behaviors among high-risk, poly-drug-using youth. Thailand has one of the highest rates of alcohol consumption in the world, ranking 6th for spirits consumption. Youth (aged 15-20) are disproportionately represented among heavy drinkers. In response to these high levels of alcohol consumption and its associated harms, the Thai Government has recently prohibited all alcohol-related advertising and increased the legal drinking age in an alcohol control bill, enacted in December, 2006, to reduce alcohol availability to youth. We propose combining data from our previous study of high-risk Thai youth with two new cross-sectional surveys that would be collected post-enactment of the policy shift. The study aims are: 1) to examine alcohol consumption and dependence patterns of high-risk, under-aged Thai youth before and after the enactment of a new, restrictive alcohol control bill;2) to examine the associations between the new, restrictive alcohol control bill with alcohol-related sexual risk behaviors and prevalent HIV, gonorrhoea, and Chlamydia among high-risk under-aged youth;and 3) to explore the meaning and culture of drinking (e.g., social norms) as related to sexual risk behaviors among high-risk under-aged youth in Thailand over time. The legal changes in combination with our previous work in Chiang Mai provide us with a unique opportunity to evaluate the effects of this natural experiment on HIV/STIs and sexual risk behaviors. Both quantitative and qualitative data collection measures will be utilized in examining the effects of this }natural experiment} on alcohol-related sexual risk among high-risk youth. We will utilize three sources of data to achieve our aims: (1) a randomly selected sample (n=300) of baseline data collected with high-risk, under-aged youth (n=943) during the in the year preceding the policy shift from Chiang Mai;(2) two new cross-sectional surveys collected using the same methods as in the baseline cycle at 12- and 24- months post-enactment of the bill and advertising ban (n=300 at each cross-section), and (3) qualitative data collection with 60 (n=30 at each cross-section) youth who are heavy (n=20), moderate (n=20), and non-drinkers (n=20). We will use the social ecological model of health to frame our investigation of the effects of these structural changes on individuals, sexual relationships, drinking environments and explore cultural factors related to alcohol-related sexual risk taking behaviors among high-risk youth. PUBLIC HEALTH RELEVANCE: The proposed study will explore the effects of a stringent new alcohol control bill in Thailand on HIV and sexual risk behaviors among high-risk, poly-drug-using youth. Guided by the social ecological framework of health, the study will utilize quantitative and qualitative methods in exploring alcohol consumption and sexual risk behaviors are multidimensional and influenced by the individual, interpersonal, cultural, and structural factors.